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Charcoal Rot Severity and Soybean Yield Responses to Seeding Rate and Row Spacing
Alemu Mengistu1, Quentin Read2, Partson Mubvumba3
1Crop Genetics Research Unit, United States Department of Agriculture, Agricultural Research Service (USDA-ARS), Jackson, TN 38301, U.S.A.
Plant Disease
|July 24, 2026
Summary
Optimizing soybean production involves adjusting seeding rates (SdRt) and row spacing (RwSp) to manage charcoal rot. Using moderately resistant soybean genotypes with high SdRt and low RwSp can increase yields and reduce disease severity.
Area of Science:
- Agronomy
- Plant Pathology
- Genetics
Background:
- Soybean production is significantly impacted by agronomic practices like seeding rate (SdRt) and row spacing (RwSp).
- The influence of these practices on charcoal rot severity, caused by *Macrophomina phaseolina*, and subsequent soybean yield remains unclear.
- Understanding these interactions is crucial for effective disease management and yield optimization.
Purpose of the Study:
- To evaluate the impact of row spacing (RwSp) and seeding rate (SdRt) on charcoal rot severity in soybeans.
- To determine how these agronomic practices affect soybean yield performance.
- To investigate potential interactions between RwSp and SdRt in influencing disease severity and yield.
Main Methods:
- A three-year field study was conducted in *M. phaseolina*-infested fields.
- Evaluated three seeding rates (198,000, 346,000, and 494,000 seeds ha⁻¹) and three row spacings (19, 38, and 76 cm).
- Assessed disease severity and yield using two soybean genotypes: Asgrow 38X8 (susceptible) and Local Seed 4565XS (moderately resistant).
Main Results:
- Lower row spacing (19 cm) sometimes resulted in lower charcoal rot severity compared to wider spacing (76 cm).
- Row spacing effects on yield were variable but generally favored lower spacing for higher yields when significant.
- Higher seeding rates (494,000 seeds ha⁻¹) showed potential for increased yields in certain conditions.
- Moderately resistant genotypes consistently exhibited lower disease severity and higher yields, especially with increased seeding rates and decreased row spacing.
Conclusions:
- Soybean growers can benefit from using moderately resistant genotypes to mitigate charcoal rot.
- Implementing high seeding rates and narrow row spacing can enhance yields and reduce disease severity.
- Strategic combination of genotype selection and agronomic practices is key for profitable soybean cultivation in charcoal rot-prone areas.
